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The specifications of the Handy Board’s DC adapter are as follows:
- 12 volt, 500 mA DC output
- 2.1 mm inside, 5.5 mm outside diameter barrel-type plug
- center conductor negative
Most “universal” type adapters will work properly at one of their settings. Look for the yellow charge LED to light up indicating proper charge (make sure the Charge Rate switch is set to “Normal” mode).
Please be careful not to get an adapter that is overpowered. Problems have been reported using adapters that are rated for 1 to 2 amps.
Also, do not use an adapter that is underpowered or undervoltage. A 9 volt adapter will appear to work—the charge LED will light—but it won’t be able to charge the battery for more than a few minutes’ worth of power.
Finally, do not use a regulated power supply. Use inexpensive, unregulated “wall wart” type adapters only.
Advanced user adapter information
The Handy Board can make use of other, specific adapter configurations with certain caveats. The one listed above is the most versatile, so that is the official recommendation, but here are some alternatives:
- 12 volt, 500 mA AC output (same power plug). When plugged into the Serial Interface/Battery Charger board, this adapter works just like the standard one. When plugged into the Handy Board directly, however, the battery will charge at one-half of normal trickle-charge rate. This is a reasonable substitution if the recommended DC adapter is hard to locate.
- 12 volt, 500 mA DC output, center positive power plug. When plugged into the Serial Interface/Battery Charger board, this adapter works just like the standard one. This adapter is not capable of charging the battery when plugged directly into the Handy Board, however.
Basically, the serial interface has a bridge rectifier, so any polarity will work, but the HB itself has only a diode, so (a) you need center-negative or alternating current, and (b) it’s protected against reverse polarity (center-positive).